Upstream overcurrent protection for a disconnect in a motor circuit

[Steve-R]

Code requires wires serving a motor to be sized at 125% of FLA, while the breaker can be much larger. I typically use 200% of FLA to size a breaker for a motor. The wiring is protected from overload by the motor's overload protection rather than the breaker which provides short circuit protection. To me it seems logical that the disconnect should be sized the same as the wire (i.e., 125% of FLA). Is that correct, and if so where does code clarify this? Sorry, I'm on vacation and don't have my code book. For instance:

If motor FLA: 45A
125% = 56A, so a 60A non-fused disconnect is OK.
200% = 90A, so a 90A or 100A breaker could be used. Would a 100A breaker adequately protect the 60A disconnect?

 

[Steve-R]

I'm guessing 430.110 is the answer, requiring the disconnect to be sized at a minimum of 115%, so a 60A disconnect would be fine in my example above, as long as it meets the horsepower rating of the motor?

 

[raider1]

I'm guessing 430.110 is the answer, requiring the disconnect to be sized at a minimum of 115%, so a 60A disconnect would be fine in my example above, as long as it meets the horsepower rating of the motor?

Correct, 430.110(A) requires motor disconnects to be sized at a minimum 115% of the FLC rating of the motor from the Tables in Part XIV of Article 430.

Chris